Method for the production of alumina



I Roi Drawing.

k m amaycomm.-

'Beit known that I,BIRena snN, citizen 'of- Norw,ay, residing'tat 17-1 7 Oscars-Gate, *Ghri'stiania,

Norway, have in vented certain new "and useful Improve merits in Methods for the' -Productionbf Al a,

which the following i ific'ation.

If. aluminumoxid isto be pairw se...

alumi-nous solutions, such-as are obtained,

for example, by ;dissolving labradorite or I minerals containingthe same,

well known that it is diflicultto' precipitate the aluminum in such a form, that it may be readily filtered oil and washed I The inventor has now made some new discoveries of which each. in itself may give rise to improvements in the old methods and;

which, when combined, will give a specially profitable method of working.

Firstly it appears, aluminum-hydroxid with ammonia, that the precipitates deposit better and quicker when the reaction mixture is heated in an autoclave up to a temperature above 100 C. It is possible to deposit the precipitate so completely, that the limpid or clear fluid or at least the greater part thereof, may be removed by decantation. It may also be easily filtered off. The principle may be employed either by effecting the admixture of ammonia under pressure or by mixing the aluminum-solution with the ammonia at atmospheric pressure, whereupon the mixture is heated in an autoclave. treatment of the precipitate may becarried out in known ways, or better, according to the methods which will be described below. Secondly the inventor has found out, that the colloidal aluminum hydroxid, which is obtained by precipitating with ammonia,

when dried and heated to temperature of 100-200 (1., will lose its collodial structure and become an insoluble powder, which easily may be filtered off and washed. It is not necessary to heat so highly that the alkaline salts and salts of the alkaline As the result of thisdiscovery, it is apparent that pure aluminum oxid may be obtained by precipitating it inthe usual manner, whereupon the precipitate, after the first filtering, is dried and heated to temperatures between 100 and 200 C. There- Y saecificationpf Lettersl'at'cnti lP i Farm) HALvoR technically; profitable,

in acids, it is ture is run into an when precipitating .era'bly under pressure, the].

The further 1 comprises oronnisrmmajnonwny. 1 T mamon 'raonucmner nnn vrinn r v I is stirred up with water, filtered and washed 1 This second feature is: of great importance I Patented Mar.;-9,1 92O-." a pncaaoamed 0Gtober'30, 1919.: sriaim. 334,566. l 1

when f'c'ombined with'iithe" first mentionedsteps, because the "drying 'wo'uld not be mode of removing fthe greater. portion of the water from 'theptecipitate; I The combined method maybe carried out, for'example,as'follows: @In the solution of. aluminum salts, the necessary amount of ammonia is added without a' practical while stirringthe liquid. Thereaction mi-x- I autoclave and heated for about '8 hours to a pressure of 1015 atmospheres, whereupon the mass is brought into the deposition receptacle in which the greater part of the fluid is drawn ofi. After having been filteredin a suitable way, 6. 9., by suction, the precipitate is heated to, say, 150 (1, whereupon water is added, and the precipitate is washed and filtered. Y Theliquid which was filtered from the aluminum-hydroxid may be used for the decomposition of more labradorite. By heating, labradorite with the said solution (which contains an ammonium salt), prefsalts of alkali and of alkaline earths will pass into solution,' and pure aluminum silicate will be left. During this operation, ammonia is set free, which may be utilized for a new precipitation. If the decomposition of the lebradorits is effected under pressure, it is convenient to drive the ammonia into the precipita tion receptacle under pressure. The pure aluminum silicate remaining from the reaction of the liquor on the labradorite can then be treated with acid to form aluminum 1 solutions from aluminum compounds by precipitation with ammonia, which comprises the step of heating the'reaction'mass under pressure. solubility of the-soluble admixture, such as 2. The improvement in the production of alumina from .aluminous solutions, which precipitating with ammonia, drying the precipitates containingv aluminum hydrate, and heating the same to temperatures between and 200 0., in order to facilitate the subsequent washing.

3. A method of regenerating ammonia employed in the precipitation of aluminum 1 hydrate, which'comprisesheating 1- erated ammonia into a precipitation bath trate from'the aluminum hydroxid precipitation, which filtrate contains ammonium salts, together with easily decomposable aluminum silicates containing alkali metal compounds and alkaline earth metal compounds, whereby the ammonia is driven out while the alkalis and the alkaline earths pass into solution, and aluminum silicate is j left. p 4 1n the process of claim 3,the improvement which comprises conducting the regencont'aining aluminum salts in solution, such operatlon be ng efl'ected under pressure.

Y 5. A methodyofftreating materials 0on5 'tainingflabradorite, which comprises boiling the said material with a solution containing an ammonium salt, under superatmospherlc pressure, thereafter reacting uponthe resis 7 due orsuch operationlwith an acid capable of dissolving at'least a substantial part of 'fthe aluminum content of the labradorite, passing into the solution formed in said last mentioned stepwhile under pressure, the ammonia regenerated in said first mentioned to precipitate aluminum hydroxid in a readily separable condition, separating the aluminum .hydroxid from the bulk, of the liquor and returning" the said liquor to the v first step of the process, drying the precipi tate containing aluminum hydroxid and 1 j YI I'BG R FJE DH'AW RSEN 

